TCP is a protocol layer on top of IP - whatever version. IP doesn't know
about ports - only protocols. So yes, your diagnosis is correct, the TCP
running on IPv4 is a different stack that running on IPv4. So Domino
LDAP is bound to all of your IPv4 interfaces and slapd to all of your
IPv6 interfaces.

I had a weird one a while back with LAMP on a recent deb install
running Linux vserver. The guest machines' daemons could not bind
to their own addresses (mysql,apache,sshd), since the host machine
had grabbed all IPv4 and IPv6 bindings.
For the record, a liberal application of chbind(8) on the host
solved the problem toute suite without having to fart around with
a myriad of daemon config files. Very handy for sys admins under
stress to complete quickly and deliver on time.
cheers
rickw
--
_________________________________
Rick Welykochy || Praxis Services
Blessed are the cracked for they let in the light.
-- Spike Milligan